Manufacture of motor fuel



Feb. 16, 1943. L R. sTRAwN MANUFACTURE 0F MOTOR FUEL l Fileg April 6, 1940 All sulla. ATTORNEYS LYNN R. STRAwN INVENTOR BY@ A) All.

HIS

4normal butylenes, including Patented Feb. i6, i943 MANUFAGTURE 0F MOTOR. FUEL Lynn R. Strawn, Port Arthur, Tex., assgnor, by mesne assignments, to The Texas Company, New York, N. Y., a corporation of Delaware Application April 6, 1940, Serial No. 328,195

11 Claims.

This invention relates to the manufacture of (CL 19E-10) i motor fuel and particularly to its manufacture from a hydrocarbon fraction comprising saturated and unsaturated hydrocarbons having four carbon atoms per molecule.

Broadly the invention comprises a process which involves segregating a C4 hydrocarbon fraction, such as obtained in the stabilization ofcracked naphtha, into a cut containing branched chain hydrocarbons and a cut containing straight chain hydrocarbons. The branched chain cut is subjected directly to alkylation, while the straight chain cut is subjected to polymerization to remove olen constituents by polymerization. The unconverted hydrocarbons are further treated to remove remaining olefln constituents to produce a straight chain hydrocarbon cut consisting essentially of normal butane. This normal butane is then converted to isobutane and the resulting isobutane utilized for alkylation with the oleiin hydrocarbons by contact with a suitable alkylation catalyst.

In accordance with the invention cracked naphtha is subjected to stabilization to remove propane and lighter constituents. The stabilized naphtha is then subjected to fractionation to remove a traction comprising C4 hydrocarbons. namely iso and normal butane, isobutylene and butylene-l and butylene-Z. v

ThisCi hydrocarbon fraction is then subjected to further fractionation to separate it into a cut containing isobutane, isobutylene and butylene-l, and another cut containing normal butane and butylene-2. The branched chain cut contains butylene-l since the boiling point of the latter is only slightly lower than that for isobutylene'. This branched chain hydrocarbon cut is passed directly to an alkylation plant.

The straight chain hydrocarbon cut is subjected to polymerization so as to convert at least a substantial proportion of the butylene-2 to normally liquid hydrocarbons, which are subsequently removed as polymer gasoline. The remaining straight chain hydrocarbons, retaining some olefin hydrocarbons, are then subjected to extraction with concentrated sulphuric acid, advantageously a portion of the catalyst used in the alkylation plant, to absorb the retained oleiin.

'I'he acid and absorbed hydrocarbons are then passed to theA alkylation plantwhile the remaining normal butane, substantially free from olefin. is subjected to isomerization. The resulting isobutane is then utilized in the alkylation plant for alkylating the olefin hydrocarbons to produce normally liquid hydrocarbons of high anti-knock value.

The object of the invention is to eiect alkylation of olen hydrocarbons with isobutane in the substantial absence of straight chain-hydrocarbons and particularly normal butane. Normal butane is unreactive in the alkylation reaction. Its presence in that reaction results in a substantial reduction in the yield of alkylated hydrocarbons and also causesl substantial deterioration of the catalyst.

A further object of the invention is to segregate the normal butane contained in the hydrocarbon feed in a relatively pure form sothat it may be eectively isomerized to isobutane without substantial deterioration of the somerization catalyst. It .has been found that in isomerizing normal butane by contact with aluminum chloride as a catalyst it is desirable to eii'ect the isomerization reaction in the substantial absence of the oleiin hydrocarbons. The olen hydrocarbons tend to react with the catalyst to form complex compounds which, in themselves, are ineffective as catalysts, at least relatively so, and whose presence soon renders the metallic halide catalyst ineffective. i

'In order to describe the invention more fully reference will now be made to the accompanying drawing showing a diagram of ilow suitable for carrying out the process.

As'indicated in the drawing, a cracked naphtha. such as obtained in the cracking of gas oil or topped crude, is conducted from a source not shown through a pipe l to la stabilizer 2. The stabilization is eiiected under conditions of temperature vand pressure adapted to remove pro. pane and more volatile constituents, so as to produce a stabilized naphtha. The propane and lighter constituents are discharged through a pipe 3. The stabilized naphtha, comprising C4 hydrocarbons and higher molecular weight hydrocarbons, are drawn 0E through the pipe 3A to a fractionator 4 wherein conditions are maintained so as. to vaporize and remove from'the stabilizednaphtha a fraction comprising C4 hydrocarbons,

including saturated and unsaturated hydrocarbons both of branched chainv and straight chain structure.

The resulting debutanized naphtha is withv drawn through a pipe 5 for such further, treatment as may be desired.

The fraction comprising gaseous C4 hydrocarbons is drawn oi! through a pipe 6 to a fractionaa tor 'I wherein it is separated into a branched chain hydrocarbon cut containing isobutane, isobutylene and butylene-l, and a straight chain hydrocarbon cut containing normal butane and butylene-2.

. The straight chain hydrocarbon cut is passed through a pipe 8 to a polymerization unit 9 `wherein the hydrocarbons are subjected to contact with a polymerization catalyst, such as phosphoric acid, at a temperature of around 400 F. and under a pressure of around 750 pounds. 'I'he operation is advantageously effected in the liquid phase, although it is contemplated that the conditions of temperature and pressure may be varied as desired. The polymerization is carried out under conditions such that at least a `substantial proportion of the butylene present in the feed mixture is converted to polymer suitable as a component of gasoline or motor fuel.

From the polymer unit the-.treated hydrocarbons pass through a pipe I to a stabilizer II wherein low boiling constituents, including normal butane andA some olefins, are removed and discharged through a pipe I2. 4The stabilized polymer gasoline is discharged-through a 'pipe I3 for such further treatment as may be deemed appropriate,

The hydrocarbons passing through the pipe I2 are conducted to an absorber I4. Inthe absorber I4 the hydrocarbons are subjected to contact with concentrated sulphuric acid. The acid may be fresh acid or used acid withdrawn from the alkylation stage of the process. `The purpose of the absorption step is to selectively absorb olefin hydrocarbons associated with the normal butane passing from the stabilizer I I.

The acid containing absorbed olens is with-- drawn through a pipe I5 and passed to an alkylation plant I6,

` The normal butane, now substantially free from olfln hydrocarbons, is passed from the upper portion of the absorber Il through a pipe I'I to an isomerization unit I8. In the unit I8 the normal butane is subjected to contact with a catalyst comprising a metallic halide, such as aluminum chloride, in the presence of a small amount of hydrogen halide, such as'- hydrogen chloride. The isomerization is advantageously effected in the gas phase at a temperature of around 150 to 250 F. and, preferably, at around 210 to 220 F., with a timeof contact of around 1 to 5v minutes. 'I'he hydrogen halide promoter is introduced tothe reaction in the proportion of around 1 to 5% by weight of the butane charge.

Under these conditions around 50 to 55% by volume of the normal butane is converted to isobutane without substantial cracking and with- `out substantial deterioration of the catalyst.

Thus, the cracked products produced will not exceed around 3% by volume of the butane charge.

The resulting isobutane is conducted through a pipe. I9 to the alkylation unit I6, previously mentioned. I

The branched chain hydrocarbon cut containing isobutane, isobutylene and butylene-l, produced from the fractionator 1, is also passed through a pipe 20 to the alkylation unit I 6. In the'alkylation unit the olefin hydrocarbons are subjected to alkylation with the isobutane by contact with an alkylation catalyst, namely, sulphuric acid having a concentration in the range 90 to 100% H2804. The temperature of reaction is maintained in the range -about 40 to 125 F. and preferably around 60 to 80 F., with a time erably about 20 to 60 minutes.

The isobutane and olfln hydrocarbons are charged to the alkylation lunit so as to maintain a substantial excess of isobutane, for example, a ratio of isobutane to olens of between about 3:1 and 5:1 or o ver. Lower ratios may be employed but in excess of 1:1.

' The resulting alkylated hydrocarbons are withdrawn through a pipe 2| for further processing as may be deemed necessary t0 render them suitable as merchantable gasoline.

As indicated, a stream of used or partially spent catalyst is withdrawn from the unit through a pine 22 and passed to the previously mentioned absorber I4 for absorption of butylene-2 and the like from the hydrocarbons passing from the polymerization unit 9. The fresh concentrated acid may be introduced to the system through the pipe 22, as indicated, or, if desired, it may be introduced directly to the alkylation unit I6.

While concentrated sulphuric acid has been mentioned as a suitable alkylation catalyst, it is, of course, contemplated that other liquid alkylation catalysts may be employed, as, for example, a catalyst prepared by passing BFa into water to complete saturation, producing a complex having the formula BFaJLHzO, where 11. has a value ranging from about 1 to 1.5.

Obviously many modifications and variations of the invention,` as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims. I

I claim:

1. A process for the manufacture of high antiknock gasoline hydrocarbons from a hydrocarbon fraction containing mainly C4 saturated and unsaturated hydrocarbons, which comprises fractionating said fraction into an iso C4 out containing isobutane, isobutylene and butylene-l, and a normal C4 cut containing normal butane and butylene-2, passing said iso C4 cut to an' alkylation zone wherein it is subjected to contact with a liquid alkylation catalyst, subjecting the normal C4 cut to polymerization such that butylene-Zv is converted to polymer liquid, withdrawing the polymer liquid, subjecting the unconverted normal C4 cut to contact with a stream of said alkylation catalyst in an absorption zone so that remaining butylene-2 is absorbed, removing the unabsorbed butane', passing the absorbed butylene-2` to said alkylation zone, and alkylating isobutane with said absorbed butylene-2 and oleilns of said iso C4 cut in said alkylation zone in the presence of said alkylation catalyst and in the substantial absence of normal butane such 66. that substantial conversion to high anti-knock gasoline hydrocarbons is secured.

2..'-The method according to claim 1 in which thev alkylation catalyst comprises concentrated sulphuric acid.

3. A process for the manufacture of high anti-A knock gasoline hydrocarbons from a hydrocarbon fraction containing mainly C4 saturated and unsaturated hydrocarbonawhich comprises fractionating said fraction into an iso C4 cut containing isobutane, isobutylene and butylene-l, and a normal C4 cutcontaining normal butane and butylene-Z, passing said iso C4 cut to an alkylation zone wherein it is subjected to contact with a liquid alkylation catalyst. subjecting the normal C4 cut to polymerization such that butylene-2 is converted to polymer liquid, withdrawing the polymer liquid, subjecting the uncon- ,verted normal C4' cut to contact with a stream of said` alkylation catalyst in an absorption sone so that remaining butylene-2 is absorbed, removing the unabsorbed normal butane, subjecting the removed btane to isomer-ization by contact with.

an isomerization catalyst in the substantial absence'of oleiina, passing the resulting isobutane and the absorbed butylen-2 to said alkylation zone, and subjecting the absorbed butylene-2 and the olefin hydrocarbons of said iso C4 cut to reaction with isobutane by contact with said alkylla-` tion catalyst in said alblation sone in the substantial absence lof normal butane such that sub.. stantial conversion to high anti-knock gasoline hydrocarbons is secured. a

4. A process for the Ymanufacture of high antiknock gasoline hydrocarbons from a hydrocar han fraction containing mainly C4 saturated and unsaturated hydrocarbons, which comprises fractionating said fraction into an iso C4 cut containing isobutane, isobutylene and butylene-l,

yand a normal C4 cut containing normal butane and butylene-2, passing said iso C4 cut toan alkylation zone, subjecting the-normal C4 cut to polymerization such-that butylene-2 is converted to polymer liquid, withdrawing 'the polymerI liquid, subjecting the unconverted normal C4 hydrocarbons to contact with a stream oi' concentrated sulphuric acid so that remaining butylene-2 is absorbed while normal butane remains unabsorbed, introducing the acid and absorbed butylene2 to the alkylation zone, subjecting the unabsorbed normal butane to isomerization in the substantial absence of oleiins soas to eif t conversion to isobutane, passing the resul isobutane to said alkylation zone, and subjecting the isobutane and the absorbed buty1enc-2 and. the olenn hydrocarbons of said iso C4 cut in said alkylation zone to reaction by contact with concentrated sulphuric acid in the substantial iccted to isomerisation in the substantial absence ofolei'ins toproduce isobutane andthe resulting isobutane utilized in the alkylation reaction.

'1. AA process for the manufacture of high antiknock gasoline hydrocarbons from a hydrocarbon fraction containing mainly C4 saturated and un- 'saturated hydrocarbons which comprises fracleave a puriiied normal butane, the acid, and absorbed butylene to said alkylation sone,

tionating said C4 fraction into an iso C4 cut containingisobutane, isobutylene and butylene-l and anormal C4 cut containing normal butane and butylene-2, passing the iso C4 cut to an alkyl- `ation sone, subjecting said normal C4 cut to separate vtreatment including contact with a.

polymerization catalyst to partially polymerize and remove butylene-2 as polymer liquid, and

'then contact with sulfuric acid to absorb and remove remaining,- butylene-2 in said cut and subjecting said puried normal butane to contact with an isomerizaticn catalyst under isomerizing conditions and in the substantial absence of oleiins thereby forminglisobutane, passing the resulting isobutane to the alkylation zone and reacting the isobutane with'the absorbed .butylene2 and the olefins of said' iso C4 ,cutin the presence of concentrated sulfuric acid in said alkylation zoneand in the substantial absence of normal butane such that substantial conversionto high antiknock gasoline hydrocarbons is secured.

' 8. A process for the manfacture of highantiknock gasoline hydrocarbons from a hydrocarbon fraction containing mainly C4 saturated arid unlsaturated hydrocarbons, which 'comprises separating said hydrocarbon traction into an iso C4 cut containing isobutane, isobutylene and butyl` ene-1, and a normal C4 cut containing normal butane and butylene-2. subjecting said normal C4 cut to catalytic polymerization to partially convert butylene-S to polymer liquid, separating the polymer liquid from the remaining unconverted absence of normal butane auch that substantial conversion to high antifknock gasoline hydrocarbon; is secured. J

5. A process for the manufacture of high antiknock gasoline hydrocarbons from a normally gaseous hydrocarbon fraction comprising C4 olefins and paramns of branched and straight chain structure, which comprises separating said fraction into a cut comprising branched chain hydrocarbons and a cut comprising straight chain hydrocarbons, subjecting the straight chain cut to polymerization so that olei'in constituents are converted to normally liquid hydroa normal .C4 cut, subjecting said remaining unconverted normal C4 cutto contact with an absorpcarbone, removing the converted hydrocarbons,

y employed'as the low-boiling tion liquid to absorb remaining butylene-2 therefrom, separating said absorbed butylene-2 from resulting unabsorbed normal butane, and alkylating a low-boiling isoparamn with said absorbed butylene-2 in the presence of an alkylation catalyst and in the substantial absence of normal butane to produce anti-knock value.

wherein the unabsorbed normal butane is subiected to catalytic isomerization in the substantial absence of olenns to thereby convert normal butane to 'isobutane, and resulting isobutane is isoparailin ,in the said alwlation step.

l0. 'I'he method in accordance with claim 8. wherein the iso C4 cut is also supplied to the said alkylation step, whereby isobutane of said iso C4 cut is alkylated with the absorbed butylene-2 and the oleilns of said iso C4 cut.

11. The method in accordance with claim 8, wherein' the said alkylation catalyst isa liquid, and the said liquid catalyst is employed as the absorption liquid in said absorption step.

LYNN R. STRAWN.

gasoline hydrocarbons of high 9. The method in accordance with claim 8,. 

